SEOUL, Dec 25 (Reuters) A South Korean democracy built a generation ago through blood, sweat and tear gas has matured, and now many believe the presidency should too.

A growing number of academics and policy makers say it is now time to drop the single five-year presidential term laid down to ensure a steady political succession in a land where change at the top had typically come only through a coup or an assassin's bullet.

''Democracy in South Korea is now strong enough that we can rest assured that a two-term presidency will not cause one-man rule any more,'' the Korean Constitutional Law Association said in a report.

In November, it released a draft bill to set up a system based on the US model of two four-year terms.

Analysts say that the current system is undermining the authority of the executive branch because one-term presidents have tended quickly to become lame ducks.

Some credit the unpopular current president, Roh Moo-hyun -- his approval rating is currently below 15 percent -- for paving the way for a change to two-term rule.

They say Roh has removed vestiges of one-man rule by cleaning up the election process and giving more autonomy to prosecutors and tax officials, used in the past by the executive branch to keep opponents in check.

''Even with so many failures and his low approval ratings, one of the achievements of the Roh Moo-hyun presidency has been more transparency and reducing the one-sidedness of a so-called imperial presidency,'' said Lee Nae-young, a political science professor at Korea University.

''But in that process, he undermined his authority,'' Lee said.

Proponents of a constitutional change argue that presidents with a chance to serve two terms could more freely pursue long-term policies, such as the complex issue of eventual unification with the communist North.

PRECIPITOUS PRESIDENTIAL POWER With just a year left in office, Roh is seen by most South Koreans as having failed to implement consistent policy to cool down an overheated real estate market, foster economic stability or bring North Korea to heel for its defiant actions.

His tumbling popularity is not unique to his presidency.

All recent South Korean leaders have seen their approval rating fall precipitously by the fourth year of their term.

Analysts blame the one-term presidency, in part, for this and for South Korea's chaotic political party system.

Typically before a presidential election, the incumbent and his party divorce.

The old party will have a shake out, or even splinter, in the hope of freeing itself from the taint of an unpopular president.

In recent weeks Roh and the ruling Uri Party have been heading for such a split.

Analysts said Uri, with an approval rate of about nine percent, might find many of its left-of-centre members looking for a new name to fight for votes in the December 2007 election.

Onme senior Uri lawmaker, Chae Su-chan, said in an email he thought most lawmakers favoured a two-term presidency.

Two-thirds approval in the unicameral parliament would be needed to set the ball rolling on a constitutional change to allow for two-term presidencies.

One leading candidate for next year's presidential election, Park Geun-hye, has said she backs the change.

Lawmakers and analysts said the most likely route would be for a candidate in the 2007 race to make two-term presidencies a policy priority, seek constitutional change, serve one term and then start the two-term system with the 2012 election.

Park, former leader of the conservative Grand National Party, is the daughter of president Park Chung-hee who took power in a military coup in 1961 and ruled until his assassination in 1979.

He was replaced by another army general, and it was only in 1987 that the country held a democratic presidential election.

Reuters DKA GC1045